UTF8Encoding.GetByteCount Method (Char(), Int32, Int32)
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Calculates the number of bytes that would be produced by encoding a set of characters from the specified character array.
Assembly: mscorlib (in mscorlib.dll)
'Declaration Public Overrides Function GetByteCount ( _ chars As Char(), _ index As Integer, _ count As Integer _ ) As Integer
Parameters
- chars
- Type:
System.Char
()
The character array containing the set of characters to encode.
- index
- Type: System.Int32
The zero-based index of the first character to encode.
- count
- Type: System.Int32
The number of characters to encode.
| Exception | Condition |
|---|---|
| ArgumentNullException | chars is Nothing. |
| ArgumentOutOfRangeException | index or count is less than zero. -or- index and count do not denote a valid range in chars. -or- The resulting number of bytes is greater than the maximum number that can be returned as an integer. |
| ArgumentException | Error detection is enabled, and chars contains an invalid sequence of characters. |
| EncoderFallbackException | A fallback occurred. |
To calculate the exact array size required by the GetBytes method to store the resulting bytes, call the GetByteCount method. To calculate the maximum array size, call the GetMaxByteCount method. The GetByteCount method generally allocates less memory, while the GetMaxByteCount method generally executes faster.
With error detection, an invalid sequence causes this method to throw a ArgumentException. Without error detection, invalid sequences are ignored, and no exception is thrown.
Note: |
|---|
To ensure that the encoded bytes are decoded properly, the application should prefix encoded bytes with a preamble. |
The following example demonstrates how to use the GetByteCount method to return the number of bytes required to encode an array of Unicode characters, using UTF8Encoding.
Imports System.Text Imports Microsoft.VisualBasic.Strings Class Example Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock) ' Unicode characters. ' ChrW(35) = # ' ChrW(37) = % ' ChrW(928) = Pi ' ChrW(931) = Sigma Dim chars() As Char = {ChrW(35), ChrW(37), ChrW(928), ChrW(931)} Dim utf8 As New UTF8Encoding() Dim byteCount As Integer = utf8.GetByteCount(chars, 1, 2) outputBlock.Text += String.Format("{0} bytes needed to encode characters.", byteCount) & vbCrLf End Sub 'Main End Class 'UTF8EncodingExample
Note: